Smoking has multiple and severe health outcomes with numerous social and health costs. There appears to be a relationship between smoking and internal stimuli such as thoughts, feelings, and bodily sensations. Negative affective states and thoughts about smoking are associated with smoking and with negative treatment outcomes. An acceptance-based approach suggests that the negative reinforcement that is offered by avoiding or escaping certain internal stimuli might be a critical process in maintaining smoking. Acceptance and Commitment Therapy (ACT) is targeted at helping clients to accept their covert experience as a means of increasing control over their overt behavior. ACT is proposed as a theoretically driven treatment linked to a specific change process in the treatment of smoking. The objectives of the proposed research are to apply ACT to the treatment of smoking cessation in a seven-week treatment protocol with a twelve-month follow up. The specific aims are to adapt and apply ACT to the treatment of smoking, to test the acceptability of ACT in the treatment of smoking, to make a preliminary evaluation of the durability of the treatment effects generated by ACT, to develop preliminary data on the active mechanism of change in ACT as a route to matching hypotheses, and to generate data to use in a power analysis of ACT in smoking cessation if further studies are warranted.